Exploit turns up heat for Firefox flaw

Computer code that could be used in cyberattacks on Firefox users has been released, increasing the urgency for people to upgrade to the latest version of the Web browser.

The two pieces of exploit code, posted online earlier this week, take advantage of a security vulnerability in Firefox that Mozilla patched in an update Thursday. In response to the exploit release, the browser maker on Tuesday upgraded the severity rating of the flaw from “moderate” to “critical,” its most serious rating.